apt-pkg/contrib/srvrec.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 /* ######################################################################
   4
   5    SRV record support
   6
   7    ##################################################################### */
   8                                                                         /*}}}*/
   9 #include <config.h>
  10
  11 #include <netinet/in.h>
  12 #include <arpa/nameser.h>
  13 #include <resolv.h>
  14
  15 #include <apt-pkg/error.h>
  16 #include "srvrec.h"
  17
  18 bool GetSrvRecords(std::string name, std::vector<SrvRec> &Result)
  19 {
  20    unsigned char answer[PACKETSZ];
  21    int answer_len, compressed_name_len;
  22    int answer_count;
  23
  24    if (res_init() != 0)
  25       return _error->Errno("res_init", "Failed to init resolver");
  26
  27    answer_len = res_query(name.c_str(), C_IN, T_SRV, answer, sizeof(answer));
  28    if (answer_len < (int)sizeof(HEADER))
  29       return _error->Warning("Not enough data from res_query (%i)", answer_len);
  30
  31    // check the header
  32    HEADER *header = (HEADER*)answer;
  33    if (header->rcode != NOERROR)
  34       return _error->Warning("res_query returned rcode %i", header->rcode);
  35    answer_count = ntohs(header->ancount);
  36    if (answer_count <= 0)
  37       return _error->Warning("res_query returned no answers (%i) ", answer_count);
  38
  39    // skip the header
  40    compressed_name_len = dn_skipname(answer+sizeof(HEADER), answer+answer_len);
  41    if(compressed_name_len < 0)
  42       return _error->Warning("dn_skipname failed %i", compressed_name_len);
  43
  44    // pt points to the first answer record, go over all of them now
  45    unsigned char *pt = answer+sizeof(HEADER)+compressed_name_len+QFIXEDSZ;
  46    while ((int)Result.size() < answer_count && pt < answer+answer_len)
  47    {
  48       SrvRec rec;
  49       u_int16_t type, klass, priority, weight, port, dlen;
  50       char buf[MAXDNAME];
  51
  52       compressed_name_len = dn_skipname(pt, answer+answer_len);
  53       if (compressed_name_len < 0)
  54          return _error->Warning("dn_skipname failed (2): %i",
  55                                 compressed_name_len);
  56       pt += compressed_name_len;
  57       if (((answer+answer_len) - pt) < 16)
  58          return _error->Warning("packet too short");
  59
  60       // extract the data out of the result buffer
  61       #define extract_u16(target, p) target = *p++ << 8; target |= *p++;
  62
  63       extract_u16(type, pt);
  64       if(type != T_SRV)
  65          return _error->Warning("Unexpected type excepted %x != %x",
  66                                 T_SRV, type);
  67       extract_u16(klass, pt);
  68       if(klass != C_IN)
  69          return _error->Warning("Unexpected class excepted %x != %x",
  70                                 C_IN, klass);
  71       pt += 4;  // ttl
  72       extract_u16(dlen, pt);
  73       extract_u16(priority, pt);
  74       extract_u16(weight, pt);
  75       extract_u16(port, pt);
  76
  77       #undef extract_u16
  78
  79       compressed_name_len = dn_expand(answer, answer+answer_len, pt, buf, sizeof(buf));
  80       if(compressed_name_len < 0)
  81          return _error->Warning("dn_expand failed %i", compressed_name_len);
  82       pt += compressed_name_len;
  83
  84       // add it to our class
  85       rec.priority = priority;
  86       rec.weight = weight;
  87       rec.port = port;
  88       rec.target = buf;
  89       Result.push_back(rec);
  90    }
  91
  92    return true;
  93 }